: The objective of this proposal is to develop a low cost, rapid, reliable and sensitive flow method to determine mutagenesis. The system is based on a CHO AL cell line, which has human chromosome 11. Mutations in chromosome 11 are detected by loss of expression of surface antigens encoded on chromosome 11. The hypothesis is that mutations in chromosome 11 can be accurately, sensitively and rapidly detected by flow cytometry based on the loss of surface antigens. The specific aims of this proposal are to develop optimal methods for staining CHO AL cells with antibodies to measure the presence or absence of S1 antigen: determine the sensitivity of the flow cytometry mutagenesis assay; validate the assay by comparing mutant fractions measured with flow cytometry to that found by the standard assay; and identify design parameters for a small, reliable inexpensive, high resolution, low noise, fast flow cytometer to make routine measurements of mutant frequency. The development of this methodology would allow for rapid and inexpensive screening pharmaceuticals for genotoxicity. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE